1. Field of the Invention
The present invention generally relates to an angular velocity sensor, and more particularly, to an angular velocity sensor in which a package for housing a vibrator is mounted on a mounting portion and is covered with a cover.
2. Description of the Related Art
An angular velocity sensor is a sensor that senses an angular velocity in rotation, and is used in systems for image stabilization of cameras, for automotive navigation, for stability control of vehicles or postures of robots, and the likes. FIG. 9 of Japanese Patent Application Publication No. 2003-28647 (hereinafter referred to as Document 1) discloses a technique in which a mounting portion (a base portion 55a) and a cover (a cover portion 55b) of a pin-mounting-type angular velocity sensor are made of a metal.
The angular velocity sensor has a vibrator, and a vibrating mode thereof senses an angular velocity. An impact conveyed to the vibrator may cause the angular velocity sensor to malfunction. In order to reduce unnecessary vibration externally applied, the vibrator is housed in a package. A certain application may require the sensing axis of the angular velocity to be almost perpendicular to a surface on which the angular velocity sensor is mounted. When the sensing axis of the angular velocity is in a side direction of a package, as shown in FIG. 1 of Japanese Patent No. 3807404 (hereinafter referred to as Document 2), a side surface of the package (a case 30) is fixed to a resin mounting portion (a mounting portion) so that the sensing axis of the angular velocity is in a direction vertical to the mounting portion (a mounting surface of the angular velocity sensor). Thus, the package is arranged vertically. Further, the package is covered with a cover 59 for protection purpose.
Recently, there has been an increasing demand to mount an angular velocity sensor on a surface of a mounting substrate so as to reduce the density of mounting. When the mounting portion (the base portion 55a) is made of a metal as described in Document 1, a terminal for surface mounting should be used together with an insulating portion in order to insulate the terminal for surface mounting from the mounting portion. The insulating portion increases the fabricating cost and the height of the angular velocity sensor. Another isolation is needed when the mounting portion made of a metal as described in Document 1 is applied to the arrangement described in Document 2 in which the vibrator is housed in the package in order to reduce unnecessary vibration, and the sensing axis of angular velocity is almost perpendicular to the surface on which the angular velocity sensor is mounted. More specifically, the above isolation mutually insulates interconnections for connecting terminals of the package (a case terminal 37 in FIG. 7 of Document 1) and terminals provided on the mounting portion and used for making external connections (terminals 45 through 49 in FIG. 12 of Document 1). The above insulation increases the fabricating cost.
The mounting portion formed with resin disclosed in Document 2 reduces the fabricating cost, as compared to that formed with metal and used together with the insulating portion. Besides, it is possible to use resin and easily insulate the interconnections for connecting the terminals of the package (the case terminal 37) and the terminals provided on the mounting portion (the terminal 45 through 49) and used for making external connections. However, an engaging portion 60 of the cover is folded down on a dent portion 58 of the mounting portion in order to fix the cover to the mounting portion as in FIG. 3 of Document 2. It is preferable to fix the cover to the both sides of the mounting portion. This fixing causes the engaging portions 60 to be folded in different directions, and needs an increased number of fabricating steps. Further, the mounting portion made of resin may be damaged by impact at the time of folding the engaging portion 60. The mounting portion is required to be thick in order to restrain the damage. The dent portion 58 should be formed so as to realize the leveled bottom of the mounting portion. The above requirements complicate the fabricating process and increase the fabricating cost.
As described above, in the angular velocity sensor, there is a demand for inexpensively fixing the cover to the mounting portion made of resin having the terminals for making connections with the package and those for making external connections. Particularly, as in the case described in Document 2, the cover is made of a metal for shielding, while the mounting portion is mainly made of resin. Thus, the process of fixing the cover to the mounting portion is complicated.